Method for improving the strength of artificial insolubilized protein filaments



Patented Dec. 26, 1950 METHOD FOR IMPROVING THE STRENGTH OF ARTIFICIAL INSOLUBILIZED PROTEIN FILAMENTS David Traill, Ardrossan, and George K. Simpson,

Fairlie, Scotland, assignors to Imperial Chemical Industries Limited, a corporation of Greatv Britain No Drawing. Application August 23, 1948, Serial No. 45,794. In Great Britain December 22, 1947 8 Claims. (01. 8-127.6)

The present invention is concerned with the provision of a method for improving the strength of artificial insolubilised protein filaments particularl of the kind wherein the insolubilisation of the coagulated filaments obtained by wet spinning is carried out by means of formaldehyde in the presence of an acidified strongly saline solu- The invention is especially applicable to insolubilised filaments produced from alkaline solutions of casein and alkaline solutions of vegetable globulins, for instance, peanut globulins or soya bean globulin solutions in dilute sodium hydroxide solution.

The object of the present invention is to increase the strength of the insolubilised rotein filaments so as to permit them to be readily proc essed in the existing machinery employed in the manufacture of textile products.

The insolubilisation of the coagulated wet spun protein filaments can be most effectively or conveniently carried out by means of formaldehyde in the presence of an acidified highly concentrated aqueous saline solution, which may advantageously be accomplished by the use of formaldehyde in association with a concentrated aqueous solution of a saline halide acidified. with hydrochloric acid or sulphuric acid as described and claimed in British specification No. 513,910. The insolubilisation of the coagulated wet spun protein filaments can also be carried out according to'British. specification No. 533.952 according to which coagulated casein or vegetable seed protein filaments are treated with a concentrated aqueous solution of a salt of a hydrohalide containing formaldehyde, or a compound which will yield formaldehyde under the conditions of the treatment, a salt of a reducing sulphur acid in which the atomic proportion, reckoned on the anhydrous salt, of oxygen if present, to sulphur does not exceed 2:1, and an acid which does not oxidise the salt of the sulphur acid, and which is substantially completely ionised in dilute aqueone solution.

While it is known that stretching of the coagulated wet spun filaments previous to their insolubilisation has a beneficial effect on the strength of the insolubilised filaments obtained from these, and that the strength of the insolubilised filaments can frequently be further increased by treatments involving further stretching, such stretching processes as have heretofore been disclosed with respect to protein fibres not only do not permit the application of extensive 2 stretching but the effects produced are only relatively small.

We have now found that a very marked improvement in the strength of the filaments obtained from 'coagulated protein filaments that have been insolubilised with formaldehyde in the presence of acidified highly concentrated salt solution, and if desired washed to free them from surface and uncombined acid or formaldehyde, is obtained if the insolubilised filaments are treated under tension with an aqueous solution of an ionisable mercury salt, particularly mercuric acetate in the presence of acetic acid. Other suitable aqueous solutions are solutions of mercuric nitrate in dilute nitric acid and of mercuric chromate dissolved in water, and of mercuric acetate with sufficient sodium hydroxide to cause formation of the basic salt.

According to the present invention, therefore, the method of improving the strength of artificial insolubilised filaments of the kind hereinbefore defined comprises treating the insolubilised filaments under tension with an aqueous solution of an ionisable mercuric salt.

It has been found, for instance, that insolubilised protein filaments obtained according to either p of the processes-of specificationsNos. 513,910 and 533,952 when stretched to a maximum in a 3% solution of mercuric acetate and 0.1N acetic acid at (3. have their wet strength increased by about 200%, giving approximately maximum strengths of 16 kg./m'm. dry and 11 13 kg./mm. wet. The strengths of the untreated fibres are respectively of the order of 9.0 leg mm? dr and 4.0 kg'l/inm. wet. This effect is obtained after '/2 hour treatment in the mercuric acetate bath followed by drying and subsequent washing for /2 hour in running water and a further drying at C. before testing. The same effect is obtained if the first drying step is omitted. Optimum conditions for treatment appear to be about /2 hour at a temperature of 70 C. but increased strength is still pronounced for shorter times at lower temperatures.

The treatment according to the invention reduces the diameter of the filaments by are-8a; gives filaments having wet strength load-elongation diagrams similar to those of their dry strength diagrams and having reduced wet and dry elongations at break; gives filaments having an increase in weight equivalent to the presence of 30% mercury.

The invention is illustrated by the following examples.

Example I A solution of ground nut protein in caustic soda is extruded into a sulphuric acid/sodium sulphate coagulating bath in the usual manner. The fibres are now given a hardening treatment for 16 hours at 38 C. in a solution consisting of 960 ml. brine, 40 ml. formalin and 14 ml. sulphuric acid. The fibres are now washed free from acid and dried at 110 C. The insolubilised fibre tow thus obtained is now stretched to a maximum in a bath prepared from 3% mercuric acetate and 0.1N acetic acid and held in this position for half an hour at 70 C. The fibre is now dried at 110 C., washed and re-dried at 110 C. The strength of the fibre before treatment with the mercuric acetate is Dry 8.5 kg./mm. Wet 3.5 kg./mm. and after stretching in mercuric acetate solution the fibre strength is Dry 16.0 kg./mm. Wet 11.0 kg./mm.

Example II Insolubilised fibre obtained as described in Example I, is stretched to a maximum in a bath prepared from 3% mercuric nitrate and 0.1N nitric acid and held in this position for half an hour at 70 C. The fibre is now washed and dried.

The strength of the fibre before treatment is similar to that given in Example I and after stretching in the mercuric nitrate solution is increased to Dry 11.0 kg./mm. Wet 7.06 kg./mm.

Example III A solution of ground nut protein in caustic soda is extruded into a sulphuric acid/sodium sulphate coagulating bath as in Example I. These fibres are now given a hardening treatment for 16 hours at 38 C. in a solution consisting of 950 m1. brine, 30 ml. formalin, 40 ml. concentrated hydrochloric acid and 32.5 gm. sodium sulphide (Na2S.9H2O The fibres are now washed free from acid and dried at 110 C. The insolubilised fibre tow thus obtained is now stretched to a maximum in a bath prepared from 3% mercuric acetate and 0.1N acetic acid and held in this position for half an hour at 70 C. The fibre is now dried at 110 C., washed and re-dried at 110 C. The strength of the fibre before treatment with the mercuric acetate is Dry 8.0 kg./mm. Wet 3.0 kg/mm'. and after stretching in mercuric acetate solution the fibre strength is Dry 15.2 kg./mm. Wet 13.4 kg./mm.

We claim: 7

1. A method for improving the strength of artificial insolubilized filaments obtained from coagulated wet spun protein filaments which comprises treating the insolubilized filaments while under tension with an aqueous solution of an ionizable mercuric salt.

2. A method for improving the strength of artificial insolubilized filaments obtained from coagulated wet spun protein filaments which comprises treating the insolubilized filaments While under tension with an aqueous solution of mercuric acetate containing acetic acid.

3. A method for improving the strength of artificial insolubilized filaments obtained from coagulated wet spun protein filaments which comprises treating the insolubilized filaments while under tension with an aqueous solution of mercuric nitrate containing nitric acid.

4. A method forimproving the strength of artificial insolubilized filaments obtained from coagulated wet spun protein filaments which comprises treating the insolubilized filaments while under tension with an aqueous solution of mercuric chromate.

5. A method as claimed in claim 1 wherein the insolubilized filaments are treated at a temperature of about C.

6. A method as claimed in claim 1 wherein the insolubilized filaments are obtained from ground nut protein.

7. A method as claimed in claim 1 wherein the insolubilized filaments which are treated with said aqueous solution are obtained from coagulated wet spun protein filaments by the treatment of the latter with formaldehyde in the presence of an acidified strongly saline solution.

8. A method for improving the strength of artificial insolubilized filaments obtained from coagulated wet spun protein filaments by the treatment of the latter with formaldehyde in the presence of an acidified strongly saline solution, which comprises treating the insolubilized filaments while under tension at a temperature of about 70 C..with an aqueous solution of an ionizable mercuric salt.

DAVID TRAILL. GEORGE K. SIMPSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 998,341 Illingworth July 18, 1911 1,799,047 Jones Mar. 31, 1931 I 2,411,815 Sowa Nov. 26, 1946 2,423,261 Sowa July 1, 1947 

1. A METHOD FOR IMPROVING THE STRENGTH OF ARTIFICIAL INSOLUBILIZED FLAMENTS OBTAINED FROM COAGULATED WET SPUN PROTEIN FLAMENTS WHICH COMPRISES TREATING THE INSOLUBILIZED FLAMENTS WHILE UNDER TENSION WITH AN AQUEOUS SOLUTION OF AN IONIZABLE MERCURIC SALT. 